‘Wettest day in a century’: How does Dunedin match up with other weather events?

In Churchill St, Dunedin, water is at knee-depth in some parts, with residents planning to evacuate after sandbagging their homes. Photo / RNZ / Tess Brunton
By Melanie Earley of RNZ
Dunedin has recorded its “wettest day in a century” as rain continues to hit the Otago region – but how does the rainfall compare with other recent flooding events?
A state of emergency has been declared in Dunedin and a red heavy rain warning for North Otago, Dunedin and coastal Clutha is not due to end until 11pm on Friday.
It is the region’s first red heavy rain warning since MetService introduced its colour-coded severe weather warning system in 2019.
Since then only 15 red rain warnings have been issued nationwide – including during the Canterbury flooding in May 2021, the 2022 flooding in Gisborne and Wairoa, the 2023 Auckland floods and Cyclone Gabrielle.
Provisionally, Dunedin (Musselburgh) has just observed its second-wettest day on record with 130.8 mm from 9:00 am Thursday-9:00 am Friday. It has been their wettest day in over a century; the last time it was at least this wet in Musselburgh was in April 1923. pic.twitter.com/k7cnzu8Aji
According to Niwa, by 9am on Friday, Dunedin had experienced its wettest day in over a century with 130.8mm falling in 24 hours.
Here’s how that compares with the largest amounts of 24-hour rainfall in other red rain warning events.
The Canterbury floods saw intense rainfall over three days with severe flooding in many areas east of the eastern foothills.
Repairs took three years, with damage to roads and bridges and flooding of homes and farms.
According to Niwa’s climate summary at the time, six Canterbury areas had record or near-record high one-day rainfall totals for May.
Winchmore experienced 78mm of rain on May 30, while Akaroa had 98mm on the same day. Waipara West had 75mm the day before while Lake Tekapo experienced 107mm that day.
Hanmore Forest had 90mm of rain in 24 hours and Ashburton came in at 62mm.
In the last week of March 2022, Gisborne and Wairoa were hit by floods which caused extensive damage to the region, including washing out the Tokomaru Bay bridge, thus isolating communities.
At the time, MetService reported Gisborne was hit with “around three months worth of rain” for the region in just 24 hours.
Between 250 to 300mm of rain was recorded.
Even before the January 27 storm hit Auckland, it had been an unusually wet month – but on that day Niwa recorded 280mm of rain in under 24 hours in the city centre.
The weather caused widespread flooding and damage to Auckland and resulted in the deaths of four men – Dave Young in Onewhero, Daniel Mark Miller and Daniel Newth in Wairau Valley, and Dave Lennard in Remuera.
Many people lost their homes and flood-damaged cars had to be towed out of the city.
An internal review later found the MetService weather modelling systems did not forecast the amount of rainfall or degree of severe flooding caused by the deluge.
Cyclone Gabrielle hit the region only a couple of weeks later.
Cyclone Gabrielle battered much of the North Island, claiming the lives of 11 people and causing damage worth nearly $13.5 billion.
The heaviest 24-hour rainfall, for Whangārei in Northland, was 183.8mm between 8am on February 12 to 8am on February 13, MetService said.
Napier Airport recorded its wettest February day from 8am, February 13, to 8am February 14, measuring 175.8mm.
– RNZ